2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/229267We show that there is a bijection between the subtoposes of the classifying topos of a geometric theory T over a signature L and the closed geometric theories over L which are `quotients' of the theory T; next, we analyze how classical topos-theoretic constructions on the lattice of subtoposes of a given topos can be transferred, via the bijection above, to logical constructions in the corresponding lattice of theories.84 pagesCategory TheoryLogic03G30; 18C10; 18B25text